An automated moored system for marine biological observation was designed and applied for studying processes of marine biological production within sea ice biota in Saroma-Ko lagoon. Seasonal coverage of sea ice in this lagoon is usually between December and April. Therefore, the biological processes related with the sea ice forming and thawing are main objective of the present study.During the first year, the automated system was deployed in early December, 1994. The system was probramed to observe water temperature, salinity, underwater irradiance and in-site fluorometric intensity. Concurrently, the direct observations on bacteria community and ice algae within sea ice as well as plankton community in water column were carried out.In the beginning of the second year, the moored system was recovered in April after ice thawing. And it was deployed again in December, 1995. A time series data over 3 months has been collected successfully for covering the sea ice period. Samples obtained from the direct observation are now under processing. These observation will give fundamental information on the biological production processes within the sea ice biota.